From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2DC5AC04A68 for ; Thu, 28 Jul 2022 14:14:11 +0000 (UTC) Received: from localhost ([::1]:48010 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oH4HC-000457-7s for qemu-devel@archiver.kernel.org; Thu, 28 Jul 2022 10:14:10 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35710) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oH3k8-0006Du-OT for qemu-devel@nongnu.org; Thu, 28 Jul 2022 09:40:00 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:38375) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oH3jw-0004Fw-HY for qemu-devel@nongnu.org; Thu, 28 Jul 2022 09:39:57 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1659015587; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=O8fRSDdh56itwpv6bymC9EnUiHzkNvwsW1Jt2WyNFOY=; b=NKdgi4maRsbmIovc8apqNPMrmEgls/5D0VjQzDl+MRc7OyN+eGQMhZj2+IiRQoUsmVZuHA cErv1nXs+ojWuPzgRbMMwDh+QY1mrr/4UDX7odrlRa4REiUlp5K3CLaIFT4YN56ffI3o/V BkKaS8k1gZ64W5htQSERyN79y4c8+xg= Received: from mail-ej1-f70.google.com (mail-ej1-f70.google.com [209.85.218.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-478-adPMRNwGMLKTu52Xy3p9Ww-1; Thu, 28 Jul 2022 09:39:46 -0400 X-MC-Unique: adPMRNwGMLKTu52Xy3p9Ww-1 Received: by mail-ej1-f70.google.com with SMTP id nb10-20020a1709071c8a00b006e8f89863ceso630620ejc.18 for ; Thu, 28 Jul 2022 06:39:46 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc; bh=O8fRSDdh56itwpv6bymC9EnUiHzkNvwsW1Jt2WyNFOY=; b=qqF0+OXVP6c38/JRuxCoeGzHMnewk7QiMTwx7CUxzbNgraurLx3Toj7tlnFpbOJteU aFlUwDpz7NCXcEPzdKZzD3x53shRa05NNUZ0ZFAp8nmoAXQW3YYvgKXGzY4WqQvDqKq4 BXB5prYwJIZJy/CK9u4J8TZCt3AlY1SPmj7UPmhz1jAZoCsqRnuzLv5eL5+2JHsiUnoh Ge/zdv21QGLbTz0JXkviXXk1kZ/vn0wK5dj88eeK4RXhvE7zDYw1+GXa222ge52PAoI0 OZ0ZShpv1KOkOmaxuiiUH9E5JY9ifACpNfXvC2pPI9PrEMRN+HpjbRbEw8ust/AxNwq3 nxhg== X-Gm-Message-State: AJIora+UMD8GSDiAP15IYhFsuzMZv75jkHRlWRE1h2vZtwBGFEJ9gtfO WGQATW0ccoaXUiB314Lvk/qBPCihq4G9uN2UgUJko2XzEblenFON9YFizrI1DGgodqg4ThMe5GX mzFNvV5eSCFPzyCE= X-Received: by 2002:a17:907:6d8f:b0:72b:6b87:81f1 with SMTP id sb15-20020a1709076d8f00b0072b6b8781f1mr21379105ejc.674.1659015585010; Thu, 28 Jul 2022 06:39:45 -0700 (PDT) X-Google-Smtp-Source: AGRyM1s/TumDK537FG5djXz1bSBwhxQWMaJnruPXWMy1d+imi7PVhvQ1+iIqsVRgus5ssL0ivi3i0g== X-Received: by 2002:a17:907:6d8f:b0:72b:6b87:81f1 with SMTP id sb15-20020a1709076d8f00b0072b6b8781f1mr21379079ejc.674.1659015584437; Thu, 28 Jul 2022 06:39:44 -0700 (PDT) Received: from redhat.com ([2.54.183.236]) by smtp.gmail.com with ESMTPSA id i8-20020aa7dd08000000b0043bea0a48d0sm711603edv.22.2022.07.28.06.39.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Jul 2022 06:39:43 -0700 (PDT) Date: Thu, 28 Jul 2022 09:39:40 -0400 From: "Michael S. Tsirkin" To: Claudio Fontana Cc: Jason Wang , qemu-devel , Alex =?iso-8859-1?Q?Benn=E9e?= , Marcel Apfelbaum Subject: Re: virtio: why no full reset on virtio_set_status 0 ? Message-ID: <20220728093501-mutt-send-email-mst@kernel.org> References: <8350fff5-f8d7-11a4-9f3a-aac8b7f5a964@suse.de> <20220727112737-mutt-send-email-mst@kernel.org> <8a8475c7-c720-1aef-02bb-ca4cb3c1ff68@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8a8475c7-c720-1aef-02bb-ca4cb3c1ff68@suse.de> Received-SPF: pass client-ip=170.10.133.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Jul 28, 2022 at 11:09:15AM +0200, Claudio Fontana wrote: > On 7/28/22 09:43, Claudio Fontana wrote: > > On 7/28/22 03:27, Jason Wang wrote: > >> On Wed, Jul 27, 2022 at 11:32 PM Michael S. Tsirkin wrote: > >>> > >>> On Wed, Jul 27, 2022 at 12:51:31PM +0200, Claudio Fontana wrote: > >>>> Hi Michael and all, > >>>> > >>>> I have started researching a qemu / ovs / dpdk bug: > >>>> > >>>> https://inbox.dpdk.org/dev/322122fb-619d-96f6-5c3e-9eabdbf3819a@redhat.com/T/ > >>>> > >>>> that seems to be affecting multiple parties in the telco space, > >>>> > >>>> and during this process I noticed that qemu/hw/virtio/virtio.c does not do a full virtio reset > >>>> in virtio_set_status, when receiving a status value of 0. > >>>> > >>>> It seems it has always been this way, so I am clearly missing / forgetting something basic, > >>>> > >>>> I checked the virtio spec at https://docs.oasis-open.org/ > >>>> > >>>> and from: > >>>> > >>>> " > >>>> 4.1.4.3 Common configuration structure layout > >>>> > >>>> device_status > >>>> The driver writes the device status here (see 2.1). Writing 0 into this field resets the device. > >>>> > >>>> " > >>>> > >>>> and > >>>> > >>>> " > >>>> 2.4.1 Device Requirements: Device Reset > >>>> A device MUST reinitialize device status to 0 after receiving a reset. > >>>> " > >>>> > >>>> I would conclude that in virtio.c::virtio_set_status we should unconditionally do a full virtio_reset. > >>>> > >>>> Instead, we have just the check: > >>>> > >>>> if ((vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) != > >>>> (val & VIRTIO_CONFIG_S_DRIVER_OK)) { > >>>> virtio_set_started(vdev, val & VIRTIO_CONFIG_S_DRIVER_OK); > >>>> } > >>>> > >>>> which just sets the started field, > >>>> > >>>> and then we have the call to the virtio device class set_status (virtio_net...), > >>>> but the VirtioDevice is not fully reset, as per the virtio_reset() call we are missing: > >>>> > >>>> " > >>>> vdev->start_on_kick = false; > >>>> vdev->started = false; > >>>> vdev->broken = false; > >>>> vdev->guest_features = 0; > >>>> vdev->queue_sel = 0; > >>>> vdev->status = 0; > >>>> vdev->disabled = false; > >>>> qatomic_set(&vdev->isr, 0); > >>>> vdev->config_vector = VIRTIO_NO_VECTOR; > >>>> virtio_notify_vector(vdev, vdev->config_vector); > >>>> > >>>> for(i = 0; i < VIRTIO_QUEUE_MAX; i++) { > >>>> ... initialize vdev->vq[i] ... > >>>> } > >>>> " > >>>> > >>>> Doing a full reset seems to fix the problem for me, so I can send tentative patches if necessary, > >>>> but what am I missing here? > >>>> > >>>> Thanks, > >>>> > >>>> Claudio > >>>> > >>>> -- > >>>> Claudio Fontana > >>>> Engineering Manager Virtualization, SUSE Labs Core > >>>> > >>>> SUSE Software Solutions Italy Srl > >>> > >>> > >>> So for example for pci: > >>> > >>> case VIRTIO_PCI_STATUS: > >>> > >>> > >>> .... > >>> > >>> if (vdev->status == 0) { > >>> virtio_pci_reset(DEVICE(proxy)); > >>> } > >>> > >>> which I suspect is a bug because: > >>> > >>> static void virtio_pci_reset(DeviceState *qdev) > >>> { > >>> VirtIOPCIProxy *proxy = VIRTIO_PCI(qdev); > >>> VirtioBusState *bus = VIRTIO_BUS(&proxy->bus); > >>> PCIDevice *dev = PCI_DEVICE(qdev); > >>> int i; > >>> > >>> virtio_bus_reset(bus); > >> > >> Note that we do virtio_reset() here. > > > > > > Yes, thank you, I completely overlooked it, I noticed this in Michael's response as well. > > > > However we end up with multiple calls to k->set_status, one from the virtio_set_status call, > > and one from the virtio_bus_reset(), which is probably something we don't want. > > > > All in all it is not clear what the meaning of virtio_set_status is supposed to be I think, > > and I wonder what the assumptions are among all the callers. > > If it is supposed to be an implementation of the virtio standard field as described, I think we should do the reset right then and there, > > but maybe the true meaning of the function is another one I couldn't understand, since _some_ of the cases are processes there. > > > > And there is a question about ordering: > > > > in virtio_pci we end up calling virtio_set_status(0), which gets us k->set_status(vdev, 0), which lands in virtio_net_set_status(0) and virtio_net_vhost_status, > > which causes a vhost_net_stop(). > > > > Should we instead land in virtio_net_reset() first, by doing a virtio reset earlier when detecting a 0 value from the driver? > > > > in the scenario I am looking at (with vhost-user, ovs/dpdk, and a guest testpmd application), > > the guest application goes away without any chance to signal (kill -9), then gets immediately restarted and does a write of 0 to status, while qemu and ovs still hold the state for the device. > > > > As QEMU lands in vhost_net_stop(), it seems to cause a chain of events that crash ovs which is trying to read an rx burst from the queue, > > while QEMU is left hanging waiting forever for a response to VHOST_USER_GET_VRING_BASE issued as a result of vhost_net_stop. > > > > Just saying, I am having more success with the second ordering, but I am still studying, don't have the full picture yet. > > > Currently I'm doing (on top of Michael's patch) the following which seems to be working > (but of course this does not even being to look at the other transports, architectures etc), > just an idea to share: > > --- > hw/virtio/virtio-pci.c | 7 ++++--- > hw/virtio/virtio.c | 7 ++++++- > 2 files changed, 10 insertions(+), 4 deletions(-) > > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c > index 3189ec014d..3cbfa3ce3a 100644 > --- a/hw/virtio/virtio-pci.c > +++ b/hw/virtio/virtio-pci.c > @@ -312,6 +312,7 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val) > case VIRTIO_PCI_QUEUE_PFN: > pa = (hwaddr)val << VIRTIO_PCI_QUEUE_ADDR_SHIFT; > if (pa == 0) { > + virtio_bus_reset(&proxy->bus); > virtio_pci_reset(DEVICE(proxy)); > } > else > @@ -1941,11 +1942,8 @@ static void virtio_pci_exit(PCIDevice *pci_dev) > static void virtio_pci_reset(DeviceState *qdev) > { > VirtIOPCIProxy *proxy = VIRTIO_PCI(qdev); > - VirtioBusState *bus = VIRTIO_BUS(&proxy->bus); > - PCIDevice *dev = PCI_DEVICE(qdev); > int i; > > - virtio_bus_reset(bus); > msix_unuse_all_vectors(&proxy->pci_dev); > > for (i = 0; i < VIRTIO_QUEUE_MAX; i++) { > @@ -1960,7 +1958,10 @@ static void virtio_pci_reset(DeviceState *qdev) > static void virtio_pci_bus_reset(DeviceState *qdev) > { > PCIDevice *dev = PCI_DEVICE(qdev); > + VirtIOPCIProxy *proxy = VIRTIO_PCI(qdev); > + VirtioBusState *bus = VIRTIO_BUS(&proxy->bus); > > + virtio_bus_reset(bus); > virtio_pci_reset(qdev); > > if (pci_is_express(dev)) { > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > index 5d607aeaa0..da58ca6f86 100644 > --- a/hw/virtio/virtio.c > +++ b/hw/virtio/virtio.c > @@ -1977,6 +1977,12 @@ int virtio_set_status(VirtIODevice *vdev, uint8_t val) > VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev); > trace_virtio_set_status(vdev, val); > > + if (val == 0) { > + VirtioBusState *bus = VIRTIO_BUS(qdev_get_parent_bus(DEVICE(vdev))); > + virtio_bus_reset(bus); > + return 0; > + } > + > if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) { > if (!(vdev->status & VIRTIO_CONFIG_S_FEATURES_OK) && > val & VIRTIO_CONFIG_S_FEATURES_OK) { > @@ -2025,7 +2031,6 @@ void virtio_reset(void *opaque) > VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev); > int i; > > - virtio_set_status(vdev, 0); > if (current_cpu) { > /* Guest initiated reset */ > vdev->device_endian = virtio_current_cpu_endian(); > -- > 2.26.2 As you say this is incomplete ... bout could you share a bit more of what issue does this address? -- MST